Most Wanted challenge requires you to be shot down with vinegar on each and every ladder.
The challenge essentially makes you a fake waller: you power-up to the top-1 position and hold it until a ranker would shoot you down and then you can go to the next ladder.
The main hurdle in this challenge is that rankers generally prefer to save their vinegar_count in mid to late ladders in order to have a better chance at shooting someone down or withstanding a shot. Staying at low upgrades is also not a good option because it is generally recommended to avoid shooting +00x01 rankers.
Winning the round is not impossible but might be very hard because falling down from the top to bottom will result in big time loss.